Simple queueing

Here is the previous question for reference: National Bank currently employs a single teller to assist customers over their lunch breaks. The typical arrival rate of customers is 11 people per hour where the teller can service people at a rate of 12 customers per hour. Assuming the standard assumptions of queuing models are met, find the following?

4. National Bank (see previous problem) is considering adding a second teller to the lunch-time situation to alleviate congestion. If the second teller is added, find the following: a. The average teller utilization b. The probability that there are 0 customers in the system c. The average number of customers in line d. The average time a customer waits before it seeing the teller e. The average time a customer spends in the service system f. If the tellers are paid $15/hour, is it worth adding the second teller (Hint: answer the question by only looking at the single hour by comparing 1 vs. 2 people)